Meeting the Large-Diameter Drilling Challenges and Securing Sustainable Performance Gains Using Hybrid Bit Technology in Deepwater Gulf of Mexico

Abstract

Abstract The operator is active in drilling deepwater (DW) exploratory, appraisal, and development wells in the central and western areas of the Gulf of Mexico (GOM) where water depths exceed 4,000 ft. In this demanding application, a key step to a successful well is achieving high performance in the large-diameter surface sections of the well. This important segment can start a well ahead of the authorization for expenditure (AFE) or create setbacks and added unplanned costs. Increasing the rate of penetration (ROP) and improving wellbore quality are two essential components for reducing cost of the riserless sections of any deepwater well. Verticality must be maintained throughout the 26-in. large-diameter section to reduce casing wear and to ensure torque and drag remains minimal while drilling to deeper depths. The 26-in. hole section is drilled riserless and a high ROP generate additional savings by lowering the drilling fluid cost. The higher percentage of cuttings provides the additional equivalent mud weight so pump and dump (PAD) mud is not required. The increased ROP needs to be achieved with low vibration levels to avoid any bottom hole assembly (BHA) component failure that would necessitate an avoidable and costly round trip. The operator has previously drilled with 18⅛-in. hybrid bits in salt and sub-salt formations and has recognized the potential of hybrid bits and their ability to drill fast with stable drilling conditions. Several drilling records have been set in this hole size. Encouraged by the performance gains and better drilling efficiency of initial hybrid bit runs, the operator planned to reduce cost of their riserless drilling section in a batch drilling program in GOM. The 26-in. hybrid bit was implemented to batch drill three hole sections, each approximately 3,400 feet long. The operator was able to optimize the drilling parameters for each successive well due to growing confidence in the stable drilling environment. This enabled the drillers to increase the ROP and greatly improve time savings. The three intervals were drilled at ROP of 255, 308, and 379 ft./hr., respectively; breaking GOM field ROP records for each consecutive run with this operator. All three penetration rates have also surpassed the current world record ROP for this hole size. Subsequent 26-in. hybrid bit runs have established consistently higher ROP and have proven to be a significantly better solution when compared to polycrystalline diamond compact (PDC) bits. This paper presents the details of the performance improvements achieved through the use of large-diameter hybrid bits, compares the drilling efficiency of large-diameter PDC and hybrid bits, and discusses some important design aspects of the hybrid bit that deliver stability and steerability.